Process of producing a master plate for offset printing and the master plate so produced



United States Patent Qfiice PROCESS OF PRODUCING A MASTER PLATE FOR OFFSET PRINTING AND THE MASTER PLATE SO PRODUCED Clifford E. Herrick, Jr., Chenango Forks, and Peter T.

Woitach, Jr., Buffalo, N.Y., assignors to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware N Drawing. Filed June 9, 1958, Ser. No, 740,572

6 Claims. (Cl. 96-28) This invention relates to the art of producing copies of an orignal document. More particularly, this invention relates to a novelv process for producing a master plate to be used in an offset printing press and to the master plate so produced.

A number of processes are known for producing copies of an original document. Of these, the three most widely used are the diazotype process, the stencil duplicating process and the direct image process. Each of these processes, however, has many drawbacks.

The diazotype process is the most convenient and the most economical process of the three mentioned above, provided, however, that the number of copies required is not too large. With present equipment, the diazotype process is not too well suited for the production of a large number of copies. In addition, the image 1n a diazotype reproduction is composed of an azo dye wh ch may fade in time and the paper of the copy contains photodecomposition products and acid which may cause in time a yellow coloration and some weakening of the paper.

In both the mimeograph and the direct image processes the orignal document must be manually copied, as on a typewriter, onto a master plate. These processes are not economical unless a very large number of copies are required. The master plate used in the stencil duplicating process is very fragile, correction of errors and insertion of handwritten matter is difiicult and high quality reproduction of photographs is impossible. Storage of completed master plates is also a problem due to the flimsiness of these plates and their-large size. The storage of master plates produced by the direct image process is also a difiicult problem. After ,being run on the offset press, the plates are wet and bear a greasy black image which is prone tosmear. ,In addition, unless the typist is especially skilled, or an electric typewriter is used, the image quality on a direct imageplate is frequently uneven.

It is, accordingly, an object of this invention to pro.

vide a method of preparing a master plate for an offset printing press, involving a contact photocopying of a translucent or transparent originah'which is both convenient and rapid.

A further object of this invention is to provide a process for preparing a master plate for an offset press, whereby the plate may be rapidly produced by tanning a hydrophilic colloid wit-h a diazo compound with the aid of actinic light.

A still further object of this invention is to provide a master plate for an offset press which can be conveniently and rapidly produced by contact photoprinting and which can be used to produce many thousands of good legible copies.

Other objects and advantages of our invention will appear from the detailed description thereof given below.

Certain lighQsensitive substances, and especially diazocontaining polymers, possess the following combination of properties:

(1) They are sufficiently water soluble to be transferred from one support to another by moisteningthe receiving support. i

(2) They are capable, when in contact with certain hydrophilic colloids, of tanning these colloids upon exposure to actinic light.

(3) The diazo-containing polymers themselves are loss in the sharpness of the contours of the pattern, by

moistening the receiving support.

.In practicing our novel method, we take an original comprising a semi-opaque positive image on a translucent or transparent support such as, for example, a typewritten copy, and place it in contact with the surface of a support coated with a sensitizer comprising a diazo-containing polymer in its water soluble form and capable of being rendered water insoluble and also of tanning hydrophilic colloids upon exposure to actinic light. The original is positioned in such a manner that the surface in contact with the sensitized support is the one facing a viewer when the image is right-reading. We then expose the assembly to actinic light. A rotary-cylinder type of exposing unit widely used for exposing diazotype or blueprint materials may be used for this purpose. The exposure time required is normally no longer than 10 seconds.

After exposure, we remove the original and place the exposed sheet in firm contact with 'a moistened surfaceof a second support coated with a hydrophilic colloid which is capable of being tanned, upon exposure to light, by the water soluble form of the sensitizer employed. We

then immediately separate the two supports. A portion The final step in our process consists of decomposing the transferred sensitizer on the second sheet. be done either chemically light.

A photographic reversal of the image is thus brought about by the process of transfer since those portions of the surface of the second support to which the sensitizer has been transferred are ink-receptive, whereas the This may or by exposure to heat and/or non-image portions of the surface of the second support remain hydrophilic since no tanning material has'been transferred to these. non-image portions. A positive, 'planographic copy of the original is thus formed on the second support.

By the use of our novel process, we are able to pro- 1 a positive Ql'i nal in apduce a planographic copy ofv proximately 30 seconds.

The following specific example of the processof pro ducing a master plate according to our invention isgiven; It is to be understood, however, thatthis example is given by way of illustration and not byway of "limitation. i

Example A high, wet-strength paper base, bearing on one sur-p face a highly calendered casein-clay layer insolubilized with formaldehyde, andbearing on the other surface .a

similar calendered layer of insolubilized casein, is coated on the first side with a dope having the following composition:

0.75 part methyl ether maleic anhydride copolymer (specific viscosity-3.2)

Patented May 2, 1961 V 3 4.25 parts cellulose acetate (55.0-56.0% combined acetic acid 9.70 parts methyl Cellosolve 71.30 parts acetone The coating was then dried. The dry film had a thickness of .0004 inch.

The dry film was then coated with a solution having the following composition:

parts p-diazo diphenyl amine-formaldehyde condensation product (prepared according to the directions given in U.S.P. 2,063,631 and aged to produce a material having less than /2% solubility in water which solubility is sutficient to enable the material to be transferred according to this process) 7.9 parts isopropanol 90.0 parts of water and the coating dried.

An original, comprising a typewritten image on a translucent sheet of paper, was placed in contact with the above sensitized surface in such a manner that the surface in contact with the sensitized support is the one normally facing a viewer in the right reading position. The assembly was then exposed to the actinic light of a whiteprint machine at feet per minute.

A high, wet-strength paper similar to the paper described above was then coated with a solution having the following composition:

2.25 parts vinyl methyl ether maleic anhydride copolymer (specific viscosity 3.2)

2.75 parts cellulose acetate (55.0 to 56.0% combined acetic acid) 9.7 parts methyl Cellosolve 71.3 parts acetone and dried.

The resulting dried coating was then subjected to the action of hot, moist ammonia fumes, thus rendering the surface hydrophilic. The thus treated surface was then wetted with a solution containing 80 parts of Water and 22.3 parts of ethylene glycol and immediately placed in contact with the sensitized surface of the paper previously exposed. The assembly was run through a set of wringer rolls after which the two sensitized surfaces were immediately separated. A heavy transfer of sensitizer in the image areas was seen to have taken place. The paper which had received the transferred image was dried briefly and re-exposed to actinic light for a few seconds.

The resultant plate was put on an offset press and gave good copy with clean backgrounds.

The light-sensitive compounds which are soluble and whose light decomposition products are capable of tanning colloids are generally those possessing a fairly large molecule. A number of diazo compounds which can be used in our process are disclosed in U.S.P. 2,063,631 and 2,100,063.

U.S.P. 2,063,631 discloses the reaction products of diazo compounds with compounds containing a reactive carbonyl group such as the aldehydes. Among the compounds disclosed in this patent are the condensation products of the sulfate of 4-amino-1,l'diphenylamine and paraformaldehyde in sulfuric acid and the reaction product of the sulfate of 4-diazo-1,1diphenylamine with isatin.

U.S.P. 2,100,063 discloses a number of diazo compounds such as 4-amino-1( N-methyl-6-naphthalene tetrahydride 1.2.3.4) aminobenzene having the formula 4 and 4"-amino-2-carboxy-1N phenyl-4.4'diamino-l.1' diphenyl methane having the formula as having the property of tanning hydrophilic colloids.

Various hydrophilic colloids may be used in our process. Besides the vinyl methyl ether maleic anhydride copolymer shown in the example, other vinyl alkyl ether maleic anhydride copolymers such as vinyl ethyl ether maleic anhydride copolymer and those of U.S.P. 2,047,- 398, as well as gelatin, glue and the water soluble cellulose ethers are suitable.

Modifications may be resorted to within the scope of the appended claims.

We claim:

1. A process of making a master plate for an offset printing press from an original comprising a positive image on a translucent or transparent support which comprises placing the original in contact with the sensitized surface of a first base, which surface consists essentially of a diazo-containing polymer which is sufiiciently water soluble to be capable of being transferred to a moist receiving surface and which is capable of being rendered substantially completely water insoluble and of tanning hydrophilic colloids upon exposure to actinic light, exposing the assembly to actinic light, whereby the portions of the polymer exposed to the light are rendered insoluble, removing the original, wetting the surface of a hydrophilic colloid previously coated on a second base with a liquid comprising Water, said hydrophilic colloid being capable of being tanned by the decomposition products of said polymer and selected from the group consisting of gelatin, glue, water soluble cellulose ether and moist ammonia treated vinyl alkyl ether maleic anhydride copolymers, contacting the exposed sensitized surface of the first base with the wetted surface of the hydrophilic colloid on the second base, separating the two coated bases whereby the remaining soluble portions of the polymer on the first base are transferred to the second base and decomposing the transferred portions of the polymer to tan those portions of the hydrophilic colloid on said second base in contact with the transferred polymer.

2. A process of making a master plate for an offset printing press as recited in claim 1, wherein the water soluble, diazo-containing polymer is a p-diazo diphenylamine-formaldehyde condensation product.

3. A process of making a master plate for an offset printing press as recited in claim 2, wherein the hydrophilic colloid is a vinyl alkyl ether maleic anhydride copolymer.

4. A process of making a master plate for an offset printing press as recited in claim 3, wherein the vinyl alkyl ether maleic anhydride copolymer is vinyl methyl ether maleic anhydride copolymer.

5. A process for making a master plate for an offset printing press as recited in claim 1, wherein the time of exposure of the assembly to actinic light is no greater than 10 seconds.

6. A process for making a master plate for an offset printing press as recited in claim 1, wherein the original comprises a typewritten sheet of paper.

References Cited in the file of this patent UNITED STATES PATENTS 2,714,066 Jewett et a1. July 26, 1955 2,747,999 Yutzy et al May 29, 1956 2,756,163 Herrick et al July 26, 1956 FOREIGN PATENTS 761,495 Great Britain Nov. 14, 1956 

1. A PROCESS OF MAKING A MASTER PLATE FOR AN OFFSET PRINTING PRESS FROM AN ORIGINAL COMPRISING A POSITIVE IMAGE ON A TRANSLUCENT OR TRANSPARENT SUPPORT WHICH COMPRISES PLACING THE ORIGINAL IN CONTACT WITH THE SENSITIZED SURFACE OF A FIRST BASE, WHICH SURFACE CONSISTS ESSENTIALLY OF A DIAZO-CONTAINING POLYMER WHICH IS SUFFICIENTLY WATER SOLUBLE TO BE CAPABLE OF BEING TRANSFERRED TO A MOIST RECEIVING SURFACE AND WHICH IS CAPABLE OF BEING RENDERED SUBSTANTIALLY COMPLETELY WATER INSOLUBLE AND OF TANNING HYDROPHILIC COLLOIDS UPON EXPOSURE TO ACTINIC LIGHT, EXPOSING THE ASSEMBLY TO ACTINIC LIGHT, WHEREBY THE PORTIONS OF THE POLYMER EXPOSED TO THE LIGHT ARE RENDERED INSOLUBLE, REMOVING THE ORIGINAL, WETTING THE SURFACE OF A HYDROPHILIC COLLOID PREVIOUSLY COATED ON A SECOND BASE WITH A LIQUID COMPRISING WATER, SAID HYDROPHILIC COLLOID BEING CAPABLE OF BEING TANNED BY THE DECOMPOSITION PRODUCTS OF SAID POLYMER AND SELECTED FROM THE GROUP CONSISTING OF GELATIN, GLUE, WATER SOLUBLE CELLULOSE ETHER AND MOIST AMMONIA TREATED VINYL ALKYL ETHER MALEIC ANHYDRIDE COPOLYMERS, CONTACTING THE EXPOSED SENSITIZED SURFACE OF THE FIRST BASE WITH THE WETTED SURFACE OF THE HYDROPHILIC COLLOID ON THE SECOND BASE, SEPARATING THE TWO COATED BASES WHEREBY THE REMAINING SOLUBLE PORTIONS OF THE POLYMER ON THE FIRST BASE ARE TRANSFERRED TO THE SECOND BASE AND DECOMPOSING THE TRANSFERRED PORTIONS OF THE POLYMER TO TAN THOSE PORTIONS OF THE HYDROPHILIC COLLOID ON SAID SECOND BASE IN CONTACT WITH THE TRANSFERRED POLYMER. 